A tale of two cities

Is this Malmö?

Every city in every country has them: urban black holes. Places in the map which most of us only known by name, or by references (the news, stories or even urban legends). Having grown up in San José (Costa Rica), I confess to being an ignorant when it comes to places like La Carpio or Los Cuadros. I have never been there. I only know they exist because some else says they do.

Are these urban black holes places we don’t know much about, or do we actually ignore them openly? And more important: what makes these neighborhoods true dark spots in the map? Is there a way of redrawing a community so that it shows on mental maps and not just geographic ones?